**Acknowledgement**

The author thanks P. Ross, J. Elliott, A. Harestad and L. Bendell for his valuable insights to improve this manuscript. Special thanks to the Charles Darwin Foundation for the Galapagos Islands, the Galapagos National Park and the Santa Barbara Marine Mammal Centre for their support and logistic field assistance.We are indebt with S. Salazar, D. Páez-Rosas, G. Jimenez-Uzcátegui, M. Cruz, P. Martinez, G. Merlen, J. Geraci, P. Howorth and the volunteers from the Marine Mammal Center in Santa Barbara (E. Stetson, C. Powell, D. Noble, N. Stebor, D. Storz and S. Crane) for their assistance in the field work and live capture of pups. Official permits for carrying out this research and exporting of samples were given by the Galapagos National Park.
